1. Technical Field
The present invention relates to a light source apparatus, an illuminator, and a projector.
2. Related Art
As a light source apparatus for a projector, there is a light source apparatus configured to cause light beams from a plurality of light sources to be reflected by a reflection member and a concave reflection surface and incident on a phosphor layer for reduction in size of the apparatus (see JP-A-2014-82144, for example). The structure described above, however, makes it difficult to uniformly illuminate the phosphor layer.
As a light source apparatus for a projector, there is also a known light source apparatus that uses a lens integrator to uniformly illuminate a phosphor layer with light beams from a plurality of light sources (see JP-A-2013-114980, for example).
To uniformly illuminate the phosphor layer, it is conceivable to combine the reflection member and the concave reflection surface in JP-A-2014-82144 described above with the lens integrator in JP-A-2013-114980 described above. In this case, since light incident on the lens integrator needs to be roughly parallelized light, the concave reflection surface is so designed that the reflection member and the concave reflection surface form a reduction-type afocal system.
In the present specification, a reduction-type afocal system is sometimes simply referred to as an afocal system. Further, a high afocal magnification configuration means a configuration for achieving a high light beam width compression factor in Comparative Example, which will be described later, and a low afocal magnification configuration means a configuration for achieving a low light beam width compression factor. The distance between a reflection element and a reflection element member in Comparative Example directly corresponds to the afocal magnification.
Assume that a reflection member and a concave reflection surface are used to form a reduction-type afocal system. When the afocal magnification is high, a light source unit needs to be implemented with high alignment precision. The afocal magnification therefore needs to be lowered to some extent in consideration of variation in the implementation of the light source unit and other factors. A low afocal magnification, however, does not allow a sufficiently narrow width of a light beam incident on the lens integrator, undesirably allowing no size reduction of the lens integrator and other optical elements provided on the downstream side of the afocal system.